1. Field of the Invention
The invention relates to a cartridge for applying medicament to an eye from a vial-dispenser of the type which is actuated by compression of the vial between its nozzle and its bottom wall.
2. Description of Related Art
There are various dispensers which are known for applying medicament to an eye. A typical eye-drop container includes a flexible vial storage portion and a nozzle for dispensing drops of medicament into the eye by squeezing the vial between its side walls. Less common, but more precise, are accordion-like or piston-like dispensers which are actuated by squeezing the vial between a bottom wall and the nozzle so as to compress the vial in its longitudinal direction, rather than from its sides. It is these accordion-like or piston-like dispensers with which the cartridge of the present invention is particularly adapted for use. An example of a new and improved piston-like dispenser is the subject of my co-pending U.S. application Ser. No. 07/801,243 which is incorporated herein by reference.
Most people encounter difficulty in applying drops to their eyes. The eye is a very sensitive body part and individuals find it difficult to control reflexive blinking when applying drops thereto. Also, eye drop users often have poor vision. Poor vision makes it difficult to position the tip of the dropper bottle over the eye and frequently causes drops to be incorrectly applied to the nose or cheek. Additionally, elderly people often have difficulty holding a dropper bottle steady or encounter difficulty in squeezing the bottle to apply a proper quantity of the medicament.
Even if the liquid medicament is properly applied to the eye, the medicament's effectiveness is limited. The minimum volume of a drop of liquid medicament which can ordinarily be introduced into contact with an eye at one time is about 30 .mu.l. Any amount which is greater than about 25 .mu.l usually spills over the eyelid onto the cheek since this is the maximum volume which the eye can ordinarily handle. When eye drops are applied to the surface of the eyeball, blinking and natural tear flow combine to limit the time to a few minutes that liquid medicament will remain effective.
On the other hand, if medicament is applied to the cul de sac of the conjunctiva, the medicament will remain effective for a longer period of time, maximizing the benefits of applying drops of liquid medicament to the eye. This is because the conjunctiva is an area of low sensitivity and low tear turnover such that blinking and tearing are avoided. However, because of the difficulty encountered in steadying the dropper and accurately positioning it over the conjunctiva, maximizing the effectiveness of the medicament remains elusive.
U.S. Pat. No. 4,543,096 describes and illustrates an apparatus having finger-like projections which are attached to the front of an eye drop bottle to spread the eyelids apart during the eye drop dispensing process. One moveable finger is connected to a lever for both depressing the lever and simultaneously causing the eyelids to spread apart while forcing a drop from the dropper bottle. However, the apparatus described in U.S. Pat. No. 4,543,096 cannot be used with the accordion-like or piston-like dispensers which are actuated by compression in the longitudinal direction rather than from the sides. Furthermore, this apparatus will not properly expose the cul de sac.
Similarly, U.S. Pat. No. 4,531,944 depicts an apparatus for steadying the tip of a dropper over the eye and further includes a sighting hole to distract the eye. However, this apparatus does not have a means to expose the cul de sac nor keep the lower eyelid depressed.
Typical eye-drop dispensers also have the disadvantage that the force which is necessary to actuate the dispenser to emit a drop is not in the same direction as the motion which is necessary to lower the lower eyelid and expose the cul de sac. It would be desirable to have a device which actuates the dispenser with a motion which is in the same direction as that which is necessary to lower the lower eyelid.